The focus of this application is on the multiple processes and influences in a sub-Saharan African environment of high HIV/AIDS prevalence, rural Malawi, that contribute to varying degrees of risk for HIV in sexual partnerships and the variety of ways in which people manage risk by managing their partnerships. The dynamic choices that are made in terms of sexual partnerships and the formation/dissolution of unions over the life course, thus, are seen as a critical factor determining the exposure of risk for HIV and may be central aspects of how individuals cope with the HIV/AIDS pandemic in a society. But to date these processes have been under-researched. The principle aim of this application therefore is to complement an existing stratified random longitudinal social science and biomarker data collection of married women aged 15 to 49 in 1998 and their husbands on HIV/AIDS, social interactions and prevention strategies in rural Malawi, analyze adaptation in relationship patterns in response to variation in risk environment over time and regions, and investigate joint household decisions on AIDS relevant behaviors such as condom use. This research includes biomarkers in order to overcome problems in the measurement of risk behavior and its change, and longitudinal data to solve estimation problems that arise in making causal analyses of change over time when not all the characteristics of husbands, wives and the risk environments are observed. The specific aims include: (1) augment the existing data collection with a random sample of females (plus their spouses if married) age 15 to 25; (2) use multi-state population models to characterize individuals' life-courses in different marital states, changes in these life-courses over time and across different risk-environments; (3) investigate key aspects of behavioral responses as they pertain to partnership dynamics, such as initial union formation, divorce and remarriage, and sexual behaviors, including aspects of intra-household decision-making with respect to condom use, spousal communication about AIDS risk, women's status and appropriate responses; and (4) use the behavioral responses to risk environment, information provisions and social interactions to derive transition matrices conditional on these factors that can be used to simulate adjustments in life-courses and assess the implication of these behavioral responses for AIDS transmission and policy interventions. [unreadable] [unreadable]